The document outlines the historical and recent developments in microbiology, detailing significant discoveries and advancements from the inception of the field in the 17th century to modern developments in microbiology branches like bacteriology, virology, and molecular biology. It highlights key figures such as Louis Pasteur, Robert Koch, and Alexander Fleming, along with their contributions to disproving spontaneous generation and establishing the germ theory of disease. Additionally, it describes various microscopy techniques and tools employed in microbiological studies, emphasizing the evolution of these methods over time.

1. HISTORICAL AND
RECENT
DEVELOPMENTS OF
MICROBIOLOGY
M. AYISHA RAFIYA
I PG MICROBIOLOGY
ST.MARY’S COLLEGE

2. 01
03
02
04
SYNOPSIS
Scope and
developments
History and recent
developments
Spontaneous
Generation
Microscopy
05
Germ theory of
disease

3. HISTORY
1677 – Antony van Ieeuwenhoek, “Father of microbiology “. He observed for little
animalcules [ single cell organisms].
1688 - Francesco redi disproved the idea of spontaneous generation
1796 - Edward Jenner Small pox vaccination.
1850 - Ignaz Semmelweis Advised washing hands to stop the spread of disease.
1861 - Louis pasteur Disproved spontaneous generation by swan neck flask experiment
1867 - Joseph Lister Antiseptic surgery using carbolic acid
1876 - Robert koch First proof of germ theory of disease with B.anthracis .
1876 - John Tyndll Developed fractional sterilization [tyndallization]

4. 1879 – Louis pasteur fowl cholera vaccine
1881 - Walter and fanny hesse growth of bacteria on solid media [agar]
1882 - Robert koch , “koch postulates “
1882 - Paul Ehrlich deleveloped acid fast staining
1883 - Elie Metchinikoff discovered phagocytosis
1884 - christian Gram Developed gram staining technique
1885 - louis pasteur first rabbies vaccination
1887 - R.J.Petri invented petri dish
1892 - Dimitri Voinovich Ivanovski Discovery of viruses

5. 1915 to 1917 - Frederick W.Twort and Felix d’Heralle-Independently discovered
bacteriophages
1928 - Alexder Fleming Discovery of penicillin
1931 - Ernst Ruska First electron microscope discovered
1943 - Delbruck and Luria worked studies on mutation in bacteria genetic work of these
bacteria
1970 - Temin and Baltimore Discovery of reverse transcriptase in retroviruses.
1977 - Gilbert and sanger Development of DNA sequencing technique.
1997 - the largest known bacterium Thiomargarito namibiensis was also discovered.
21th century the genome of malarial parasite ,plasmodium falciparum was sequenced in 2002.
New branches of microbiology,bacteriology,Virology,Mycology,Parasitology and Immunology
developed during this century.

6. Germ theory of disease
Spontaneous generation is an obsolete body of thought on the ordinary formation of living
organisms without descent from similar organisms.
Typically, the idea was that certain forms such as fleas could arise from inanimate matter such
as dust or that maggots could arise from dead flesh.
Francesco Redi who, in the 17th century, had performed experiments based on the same
principle Spontaneous generation
Pasteur boiled a meat broth in a flask that had a long neck that curved downward, like a goose.
The idea was that the bend in the neck prevented falling particles from reaching the broth, while
still allowing the free flow of air.
The flask remained free of growth for an extended period.
When the flask was turned so that particles could fall down the bends, the broth quickly became
clouded.

7. Pasteur exposed boiled broths to air in vessels that contained a filter to prevent
all particles from passing through to the growth medium.
And even in vessels with no filter at all, with air being admitted via a long
tortuous tube that would not allow dust particles to pass.
Nothing grew in the broths unless the flasks were broken open, showing that
the living organisms that grew in such broths came from outside, as spores on
dust, rather than spontaneously generated within the broth.
This was one of the last and most important experiments disproving the theory
of spontaneous generation.

8. Germ theory of disease

9. Scope and developments of microbiology
Medical Microbiology
Microbial genetics
Physiology
Virology
Plant pathology
soil Microbiology
Industrial Microbiology
Molecular Biology

10. Medical Microbiology
Medical Microbiology involves the identification of microorganisms for the
diagnosis of infection disease and the assessment of likely response to
specific interaction.
Major catogaries involves of organisms include bacteria, mycobacteria,
fungi and parasites.
It Deal with disease of humans and animals, Identify and plain measures to
eliminate agents causing infectious disease.
Major scope of Medical microbiology Research scientist carrier in research and
developments Laboratories of pharmaceutical ,biotech, or food industries.
Also work in academic reasearch ,government agencies or reasearch institutes.

11. Microbial Genetics
Microbial genetics studies microorganisms for different purposes,
The microorganisms that are observed are bacteria and archaea.
Some fungi and protozoa are also subjects used to study in field.
The studies of microorganisms involve studies of genotype and
expression system.
The scope of genetics reaches to the problems of growth ,form and
their origin.
The usage of recombinant DNA technology is a process this work.

12. Physiology
Physiology is the study of how the human body works.
It describes the chemistry and physics behind basic body of
functions, from how molecules behave in cells to how systems of
organs work together.
They could also work as personal trainers, even for high profile
individuals after having enough experience.
They could work as physiotherapists. Apart from this ,they could
also choose to be medical lab technicians, research assistants or
clinical physiologists in hospitals.

13. Virology
Viruses that infect humans are how studied by medical virologists.
Virology in a broad subject covering biology, health, animal welfare,
agriculture and ecology.
They can choose to be a research associate, ,virologist, Assitant,etc.
They can find employment in research centres, pharmaceutical
companies, private clinics ,Human immunology laboratory,
government hospitals ,reputed colleges and universities,etc.

14. Plant Pathology
Plant pathology is the scientific study of plant disease caused by
pathogens and environmental conditions.
It involves the identification of pathogens , studying disease cycles,
and economics impacts,and managing plant disease .
Plant pathology involves the study of pathogen ,identification,
disease etiology, disease cyles,economic impact ,plant disese
epidemiology ,plant disease resistance, how plant disease affect
humans and animals ,pathosystem genetics, and management of plant
disease.

15. Soil Microbiology
Soil microbiology governs nutrient processing and reclying in
soil and also affects the decomposition of organic matter in soil,
soil salinity and soil activity ,thereby impacting soil fertility and
crop health.
Microbiologists in work a variety of settings include hospitals,
research institutions, pharmaceutical companies, and government
agencies.
They may also be employed in industries such as food and
beverage production, cosmetics, and environmental consulting.

16. Industrial Microbiology
Industrial Microbiology is the branch of microbiology engaged in the
study use and manipulation of microorganisms for commercial and
industrial significance.
It involve the use of microorganisms in the production of food
,pharmaceuticals and other industries.
In which microorganisms are used for the production of important
substance such as antibiotics, food products ,enzymes, amino
acids,vaccine and other chemicals.
scope of health care, biotechnology, reseach environmental science
,dairy science and agriculture.

17. Molecular biology
Molecular biology is a branch of biology that seeks to understand the
molecular basics of biological activity in and between cells ,including
biomolecular synthesis, modification, mechanisms and interactions .
It developments of molecular methods for the identification and
monitoring of microorganisms in natural ecosystems.broad scope
microbiology in journal covering basic to translational research.
Molecular biology conduct research and developments in a wide range
of a sectors including medicine,environmental science and agriculture.

18. MICROSCOPE
◇ A Microscope is defined as the optical instrument consisting of a
lens or combination of lens for making enlarged or magnified
images or minute objects.
◇ The science dealing with all aspects of microscope is called
as microscopy.
Microscopy is classify into two categories
Simple Microscope
Compound Microscope

19. MICROSCOPE
Light or optical
microscope
▪Bright field microscope
▪Dark field microscope
▪Fluorescence microscope
▪Phase contrast
microscope
Electron Microscope
▪Transmission electron
microscope
▪Scanning electron
microscope
Depending on source of microscope ;

20. A simple microscope is a magnifying glass that has a double convex lens
with a short focal length.
Working of Simple Microscope;
Light from the light source is made to pass through a thin object which is
transparent.
To get an enlarged virtual image, a biconvex lens is used.
For higher magnification and resolution, the lens must be close to the sample.
By viewing the details of the sample contrast can be obtained. This is done
by staining the sample.
To obtain contrast in the image, the size and intensity of the light beam can be
modified with the help of a condenser or the diaphragm.
SIMPLE MICROSCOPE

21. Uses of Simple Microscope
It is used in pedology (a study of soil particles).
It is used by a dermatologist to find out various skin diseases.
It is used in microbiology to study samples of algae, fungi etc.
It is used by the jewellers to get a magnified view of the fine parts
of the jewellery.

22. Compound Microscope
A compound microscope is defined as A microscope with a high
resolution and uses two sets of lenses providing a 2-dimensional
image of the sample.
The term compound refers to the usage of more than one lens in the
microscope. other type of optical microscope is a simple microscope.

23. Working Principle of Compound Microscope;
There are two types of lenses that are used in the compound
microscope:
The objective lens is placed close to the object that needs to be
examined.
The eyepiece allows the image to be viewed
.The light is made to pass through the thin transparent object. A
magnified image of the object is obtained by the objective lens.
This image is known as the real image.
The eyepiece or the ocular lens then magnifies the real image
more and is viewed as the virtual image.
The compound microscope is also known as the bright-field
microscope because the light passes directly through the light
source to the eye through the two lenses.

24. Parts of Compound Microscope
The parts of a compound microscope can be classified
into two:
Optical parts
Non-optical parts

25. Advantages of Compound Microscope
Due to the usage of multiple lenses, one can obtain detailed information
about the sample.
These microscopes have their own sources of light.
This microscope is user-friendly and easy to handle
Disadvantages of Compound Microscope
The magnification of the sample is possible only to a certain extent,
once this limit is reached the sample cannot be viewed.
Uses of Compound Microscope
The identification of diseases becomes easy in pathology labs with the
help of a compound microscope.
Forensic laboratories use compound microscopes for the detection of
human fingerprints.
The presence of metals can be detected with the help of a compound
microscope
.

26. Phase contrast Microscope
Phase-contrast microscopy is an optical microscopy
technique that converts phase shifts in the light passing
through a transparent specimen to brightness changes in the
image.
It was first described in 1934 by Dutch physicist Frits
Zernike.

27. Principle of Phase contrast Microscopy
The Working of Phase contrast Microscopy Partially coherent
illumination produced by the tungsten-halogen lamp is directed through
a collector lens and focused on a specialized annulus (labeled condenser
annulus) positioned in the substage condenser front focal plane.
Wavefronts passing through the annulus illuminate the specimen and
either pass through undeviated or are diffracted and retarded in phase by
structures and phase gradients present in the specimen.

29. Applications of Phase contrast Microscopy
To produce high-contrast images of transparent specimens, such as
living cells (usually in culture),microorganisms, thin tissue slices,
lithographic patterns,fibers,latex dispersions,glass fragments, and
subcellular particles (including nuclei and other organelles).
Advantages of Phase contrast Microscopy
Living cells can be observed in their natural state without previous
fixation or labeling.
It makes a highly transparent object more visible.
No special preparation of fixation or staining etc. is needed to study an
object under a phase-contrast microscope which saves a lot of time.

30. Fluorescence Microscope
A fluorescence microscope is an optical microscope that uses
fluorescence and phosphorescence instead of, or in addition to,
reflection and absorption to study the properties of organic or
inorganic substances.
Fluorescence is the emission of light by a substance that has
absorbed light or other electromagnetic radiation while
phosphorescence is a specific type of photoluminescence related to
fluorescence.
The fluorescence microscope was devised in the early part of the
twentieth century by August Köhler, Carl Reichert, and Heinrich
Lehmann, among others.

31. Principle of Fluorescence Microscope
The initial step in the observation of the sample through a fluorescence
microscope includes labelling the sample with fluorescent dyes. Then, light
source which emits white light is allowed to fall onto the excitation filter.
This filter selects the light of a specific wavelength that can excite the
fluorescent molecules tagged in the specimen and this excitation light
incidents onto the dichroic mirror.
The light after reflection from the dichroic mirror passes onto the specimen
after emerging from the objective lens.
This small wavelength light falls into the specimen stained with a fluorescent
dye that results in emission of high wavelength light which passes again
through the condenser lens and dichroic mirror.
This allows green light in maximum along with some blue light to pass
towards the emission filter.
The detector detects the green light and permits it to fall back onto the
specimen thereby, forming fluorescent green specimens against a dark
background.

33. Types of Fluorescence Microscope
Wide-field Epifluorescence microscope.
WF microscope
Confocal microscope

34. Advantages of Fluorescence Microscope ;
The great sensitivity and specificity of fluorescence microscopy
techniques are responsible for the good reliability and accuracy of
microscopic analysis. Even when performed by technicians with less
training, the likelihood of incorrect observations or discrepancies in test
interpretation is decreased
Small things are simple to see because of the comparatively bright
fluorescent picture on a dark background.
High specificity for details is achieved by using modern fluorochromes
and interference light filters.
Limitations of Fluorescence Microscope
The addition of probes and dyes to a membrane system has the ability to
alter the characteristics of the liposomal delivery system.
The selection of the fluorescent dye is an important step since some dyes
might produce significant changes in the host membrane and/or
experimental errors, leading to incorrect data interpretation.

35. Electron Microscopy
An electron microscope is a microscope that uses a beam of
accelerated electrons as a source of illumination.
As the wavelength of an electron can be up to 100,000 times shorter
than that of visible light photons.
Electron microscopes are used to investigate the ultra structure of a
wide range of biological and inorganic specimens including
microorganisms, cells, large molecules, biopsy samples, metals, and
crystals.
Industrially, electron microscopes are often used for quality control
and failure analysis.

36. PRINCIPLE
Electron microscopes use signals arising from the interaction of an
electron beam with the sample to obtain information about structure,
morphology, and composition.
The electron gun generates electrons.
Two sets of condenser lenses focus the electron beam on the
specimen and then into a thin tight beam.
To move electrons down the column, an accelerating voltage (mostly
between 100 kV-1000 kV) is applied between tungsten filament and
anode.

37. The specimen to be examined is made extremely thin, at least
200 times thinner than those used in the optical microscope.
Ultra-thin sections of 20-100 nm are cut which is already placed
on the specimen holder.
The electronic beam passes through the specimen and electrons
are scattered depending upon the thickness or refractive index of
different parts of the specimen.
The denser regions in the specimen scatter more electrons and
therefore appear darker in the image since fewer electrons strike
that area of the screen. In contrast, transparent regions are
brighter.
The electron beam coming out of the specimen passes to the
objective lens, which has high power and forms the intermediate
magnified image.
The ocular lenses then produce the final further magnified
image.

38. TYPES
There are two types of electron microscopes, with
different operating styles:
The transmission electron microscope
(TEM)
The scanning electron microscope (SEM)

39. TRANSMISSION ELECTRON MICROSCOPE
The transmission electron microscope is used to view thin specimens
through which electrons can pass generating a projection image.
The TEM is analogous in many ways to the conventional (compound)
light microscope.
TEM is used, to image the interior of cells (in thin sections), the
structure of protein molecules (contrasted by metal shadowing), the
organization of molecules in viruses and cytoskeletal filaments
(prepared by the negative staining technique), and the arrangement of
protein molecules in cell membranes (by freeze-fracture).

40. PARTS
TEM has three working parts which
include:
Electron gun
Image producing system
Image recording system

41. APPLICATIONS
To visualize and study cell structures of bacteria, viruses, and fungi
To view bacteria flagella and plasmids
To view the shapes and sizes of microbial cell organelles
To study and differentiate between plant and animal cells.
Its also used in nanotechnology to study nanoparticles such as ZnO
nanoparticles
It is used to detect and identify fractures, damaged microparticles which
further enable repair mechanisms of the particles.

42. SCANNING ELECTRON MICROSCOPE
Conventional scanning electron microscopy depends on the emission of
secondary electrons from the surface of a specimen.
Because of its great depth of focus, a scanning electron microscope is the
EM analog of a stereo light microscope.
It provides detailed images of the surfaces of cells and whole organisms
that are not possible by TEM. It can also be used for particle counting and
size determination, and for process control.
It is termed a scanning electron microscope because the image is formed
by scanning a focused electron beam onto the surface of the specimen in
a raster pattern.

43. PRINCIPLE
Unlike the Transmission Electron Microscope which uses transmitted electrons,
the scanning electron Microscope used emitted electrons.
The Scanning electron microscope works on the principle of applying kinetic
energy to produce signals on the interaction of the electrons.
These electrons are secondary electrons, backscattered electrons and diffracted
backscattered electrons which are used to view crystallized elements and photons.
Secondary and backscattered electrons are used to produce an image.
The secondary electrons are emitted from the specimen play the primary role of
detecting the morphology and topography of the specimen while the
backscattered electrons show contrast in the composition of the elements of the
specimen.

44. PARTS
Electron Source – This is where electrons are produced under thermal
heat at a voltage of 1-40kV. The electrons the condense into a beam that
is used for the creation of ana image and analysis. There are three types
of electron sources that can be used i. e Tungsten filament, Lanthanum
hexaboride, and Field emission gun (FEG)
Lenses – it has several condenser lenses that focus the beam of electrons
from the source through the column forming a narrow beam of electrons
that form a spot called a spot size.
Scanning Coil – they are used to deflect the beam over the specimen
surface.

45. Detector –
Its made up of several detectors that are able to differentiate the
secondary electrons, backscattered electrons, and diffracted backscattered
electrons.
The functioning of the detectors highly depends on the voltage speed, the
density of the specimen.
The display device (data output devices)
Power supply
Vacuum system

46. Applications
Used for spot chemical analysis in energy-Dispersive X-ray
Spectroscopy.
Used in the analysis of cosmetic components which are very tiny in
size.
Used to study the filament structures of microorganisms.
Used to study the topography of elements used in industries.

47. ADVANTAGES
They are easy to operate and has user-friendly interfaces.
They are used in a variety of industrial applications to analyze surfaces
of solid objects.
Some modern SEMs are able to generate digital data that can be
portable.
It is easy to acquire data from the SEM, within a short period of time
of about 5 minutes.

48. LIMITATIONS
They are very expensive to purchase
They are bulky to carry
They must be used in rooms that are free of vibrations and free of
electromagnetic elements
They must be maintained with a consistent voltage
They should be maintained with access to cooling systems

50. Scanning electron microscope
Transmission electron microscope

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https;//www.wikipedia.com
https;//bio.libretexts
https;//microbenotes.com
https;//ncbi.nlm.gov
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Referance

52. Thank
you